I have just installed the latest BIOS update using the Recovery method and all is well. There is an insignificant drop off in performance (crudely measured by how quickly MalwareBytes runs).
One oddity, though, and that is the DSA reported all my drivers etc. were up to date with BIOS version 0370 and exactly the same now version 0371 is on. I am not too bothered because I regularly go to the download page and check for myself but I thought someone at Intel might like to know.
Still looking forward to the Express BIOS updating method to be reinstated.